Polysaccharides were isolated from two fungi, Auricularia Wood's-ear and Flamulina velutipes, and one medicinal plant, Amaracus dictamnus, which cross-related immunologically with Type III pneumococcal polysaccharide. Mild acid hydrolysis and chromatographic separation with D.E.A.E. Sephdex yielded polysaccharides of increased activity in Ouchterlong tests with Type III pneumococcal antiserum.